This invention relates to a method of determining the amounts of contaminant remaining on surfaces of interest to an individual or an agency. More particularly, the invention relates to a method of determining when a container or any surface is sufficiently free of contaminants.
A problem associated with the use of pesticides and other materials treated as, or perceived to be hazardous, is the safe disposal of the container.
A number of the pesticides registered with the EPA instruct the user to dilute them with water prior to application to the selected target. By state and federal law, these containers must be triple-rinsed with a volume of water equal to 10-30% of the original volume, or pressure rinsed for at least 30 second before the container can be discarded. When either of these two actions have occurred, the container can be considered as non-hazardous waste. However, since it is very difficult to prove that the container has been rinsed and since extremely small amounts of residual products may cause future problems, most pesticide containers are not readily accepted in landfills. This reluctance on the part of landfills to take containers means that either state or federal programs must be established to collect, inspect and dispose of the containers. Even under these conditions it is difficult for the state or federal agents to insure that the containers are acceptable. The only way to determine that rinsing techniques have effectively cleaned the container and rendered it suitable for disposable is to analyze the water remaining in the rinsed container. For a vast majority of users such analyses are very expensive, time-consuming and impractical. This same problem of establishing that the container has been properly rinsed holds true for the homeowner who elects to safely dispose of pesticide, paint, bleach, pool chemicals or household cleaner containers.
Most programs for confirming the cleanliness of the container rely on visual inspection coupled with checking for the remnants of any solvent odors. With proper training this can be used successfully with odiferous products and those that are highly colored. Unfortunately, there are many hazardous products which are odorless and colorless.
Another method relies on analytical procedures for the detection of specific contaminants. This procedure becomes very prohibitive when several different chemicals are being used. Such analytical techniques include but are not limited to spectophotometric analysis, immunoassay techniques, gas and liquid chromatography, mass spectroscopy and nmr procedures. Thus, the difficulty being experienced by the federal, state and local officials and the consumer is the fact that there are a multitude of products requiring a proper rinse procedure and no single method of analysis available to detect container cleanliness. The various physical forms of these hazardous products such as wettable powders, flowables, emulsifiable concentrates and granulars also add to the analytical problem.
Recently, European Patent Application No. 0 327 163 suggested a means of marking products to prevent the dilution of, or the substitution of one product for another. It discloses the concept of tagging the product with a marker compound that could be analyzed for or identified by immunoassay. The patent application calls for the introduction of a marker compound to the desired product. One could later prove the validity of the sample by either analyzing the sample as is (water-based product) or first extracting the product to move the marker into a water phase and then analyzing by immunoassay.
Unfortunately, the detection method of the European Patent Application No. 0 327 163 does not provide a satisfactory solution to the problem of ascertaining whether a container is sufficiently clean so that it is ready for disposable. First of all, the method of the European Patent Application uses a marker concentration in the range of 25 ppm to 1 ppb. This concentration range represents the detection limits of the immunoassay procedure, i.e., the method has been designed to determine the concentration of the marker as originally added, not upon dilution. Thus, when a container of a product containing the marker at the prescribed level is rinsed according to the current procedures, the marker concentration in the final rinsate is reduced to much below the detectable concentration. Since a rinsed container is usually considered to be clean when 99.9999 of the original concentration of the hazardous product has been removed it is evident that the marker concentration in the rinsate would be well below any detectable level.
Secondly, the marker used in the European Patent Application is substantially water-soluble. Consequently, when the marker is used in an oil-based product it must be extracted, reduced in volume and dissolved in water or a water/methanol mixture so that the analysis can occur. This multi-step operation is tedious and cumbersome.
Thirdly, since the marker is water-soluble, unless it is used in a water-based product, it would not behave in a manner analogous to the bulk product that was being tagged. As the product was rinsed from the container the water,soluble compound would dissolve in the rinse water at a rate disproportionate from the active ingredient. This would result in a false indication of a clean container.
Lastly, the marker compounds disclosed in the European Patent Application are identified as metabolities of the EPA registered insecticide cypermethrin or meta phenoxybenzoic acid and dichlorovinyl cyclopropane carboxylic acid. Since these compounds are recognized metabolites of the insecticide cypermethrin, the presence of these compounds in crops or crop related products is regulated by the FDA. Hence using this type of compound would be in essence using a pesticide to act as a marker for another compound. In an environmentally conscious society use of such compounds is not an acceptable approach to the problem.
It is therefore an object of the invention to provide a method of determining the amount, if any, of contaminants remaining on surfaces.
Another object of the invention is to provide a method for using a single analytical procedure to monitor the successful rinsing from a container of any contaminated product designed for use with water.
Another object of the invention is to provide a simple, economically attractive method enabling both the customer and state and federal officials to easily monitor the proper removal of the specified products from containers.
Yet another object of the invention is to provide a method for accurately determining the residual amount of contaminated product remaining on a rinsed surface such as that of a container or post-harvest produce, by using a marker which behaves in a manner analogous to the tagged bulk product.
An additional object of the invention is to provide a method of monitoring the movement and concentration of a product in the environment.
A further object is to provide an assay kit with which the customer or government official can rapidly determine whether a surface is contaminant-free without recourse to laboratory facilities.